Senior Backend Software Engineer (Java/Kotlin)

Holisticon Connect is a division within NEXER GROUP - a custom software development company. We started in Poland in 2017 and are now a team of over 140 people. We have the opportunity to work with world-renowned brands from Scandinavia, the UK, and Western Europe. Our goal is to grow stronger, in competence rather than in numbers. If you like what we do, check out our offer, maybe we will have the pleasure of meeting you!

We are looking for a Senior Backend Software Engineer (Java/Kotlin) to join an international product company building a modern, cloud-native enterprise SaaS platform operating at global scale. You will join a mature engineering environment where scalable, distributed backend architectures, software reliability, strong system ownership, and long-term maintainability take priority over quick hacks. This role is built for an engineer who thrives on tackling complex architectural trade-offs, driving technical standards, and owning services throughout their entire lifecycle - from initial RFC/design through production telemetry.

We offer a choice of employment form: Employment Contract or B2B

• UoP: 23 500 - 25 000 PLN gross/month
• B2B: 170 - 180 PLN net/hour + VAT

Responsibilities

• Architect, build, and maintain high-throughput, resilient backend microservices in Java or Kotlin.
• Drive technical decisions and system design, authoring design docs (RFCs) and evaluating architectural trade-offs (scalability, latency, data consistency).
• Design and evolve robust APIs (REST, event contracts) and external integration layers for enterprise clients.
• Own the full service lifecycle: from technical conception, through CI/CD automation and automated testing, to production deployment and live monitoring.
• Continuously optimize performance, concurrency, fault tolerance, and resource utilization across distributed components.
• Foster engineering excellence through insightful code reviews, architectural pairing, and setting testing/clean code standards.
• Collaborate cross-functionally with Product Managers, Platform/DevOps, and QA engineers to translate complex business requirements into clean, decoupled domain models.
• Identify technical debt proactively and drive modernization initiatives across platform tooling and pipelines.

You might be the perfect match if you are/have

• 5+ years of professional experience in backend software development;
• Strong commercial experience with Java and/or Kotlin;
• Very good understanding of object-oriented programming, software design principles and clean code practices;
• Experience designing and developing REST APIs and backend integrations;
• Experience building and maintaining production-grade backend applications;
• Good understanding of distributed systems and modern backend architecture;
• Practical experience with relational databases and SQL;
• Strong knowledge of version control, especially Git;
• Experience with automated testing and modern software engineering practices;
• Ability to analyse technical problems, evaluate different approaches and explain architectural trade-offs;
• A strong ownership mindset and the ability to work independently;
• Fluent English and Polish for smooth collaboration in an international environment;
• Located in Poland for at least 5 years.

Moreover, we appreciate skills in these areas

• Experience with Spring Boot or other JVM frameworks;
• Experience with event-driven or distributed architectures;
• Experience with messaging or streaming platforms;
• Familiarity with Docker and Kubernetes;
• Experience with cloud environments such as AWS, Azure or GCP;
• Experience with CI/CD pipelines;
• Knowledge of observability, monitoring and production troubleshooting;
• Experience with performance optimization and high-throughput backend systems;
• Familiarity with NoSQL, search engines or distributed data stores;
• Experience working in a SaaS or product-oriented environment;
• Experience contributing to technical architecture or leading larger engineering initiatives.

By joining us, you gain the following

• Opportunity to work on exciting, international projects in cutting-edge industries like Automotive, Biotech, IoT;
• Possibility to develop in cloud technologies;
• Becoming part of a team that believes that the next step to a promising future is to put your heart into it and make it happen;
• Respect for your private life so you don't have to work overtime or on weekends;
• Team Events budget to socialize outside of work;
• Company Events to celebrate smaller and bigger successes (Summer Party, Programmer's Day, and trips abroad - so far we've been in South Africa, Are, and Barcelona).

Perks and benefits

• Fully remote work or in our office in Wrocław;
• Benefits such as Luxmed, Multisport, and life insurance in Nationale Nederlanden;
• Attractive referral system (9,5k for senior, 6k for mid, 2,5k for junior);
• Personal Training Budget with additional paid hours;
• Passion Day - an extra day off for your hobby to spend as you please;
• Flexible working hours with no micro-management approach. Our core hours are 9-15, the rest of the working time is up to you;
• We provide high-quality work equipment + 2 additional monitors and accessories.

If you apply for this position and match our expectations, then

• You will be invited to an HR Screening with our IT Recruiter.
• You will meet with a client.
• Final decision and job offer.

Submit your application online in one easy step! Apply now!

You will earn

• UoP: 23 500 - 25 000 PLN gross/month
• B2B: 170 - 180 PLN net/hour + VAT